The basic purpose of this project is to clarify the role of silicon deficiency in the etiology of atherosclerosis, and the involvement of silicon in the prevention of that disease. Silicon, shown to be essential for normal growth and development, acts as a crosslinking agent in connective tissue. Highest levels are found in arterial walls. It is intended to establish a distribution pattern of silicon in aortas and coronary arteries through scanning electronmicroscopy, histology and chemical analysis and to correlate the silicon contents with the physical properties, such as elasticity and resistance to lipid diffusion, both in normal and atherosclerotic human and animal material. Silicon deficiencies in rats maintained in a trace element controlled environment system will be studied with respect to athrosclerosis and tolerance toward dietary cholesterol. The biological potency of organosilicon compounds is being assayed to determine chemical properties which underlie biological activity. Naturally occurring organic silicon derivatives from connective tissue will be isolated, chemically characterized, and subsequently synthesized. Preventive and therapeutic trials will be carried out with these substances in animal models of atherosclerosis. The final aim is to make silicon compounds available for human trials. The role of silicon in cholesterol absorption and metabolism, lipid transport, etc. will be investigated.